Point out 8-10 weeks is bad news for him, and bad news for Team Canada. 10 weeks puts him right at the end of January, a week or so before the start of the Olympics. All things being equal Point is most likely a lock, so it probably makes sense for Armstrong to name him to the team in late December and also have a replacement in mind in the event that he's not healthy in time. Doesn't leave much time for Point to return to the ice and get back into game shape, though (if best case is 8 weeks, that's mid-January, so a week or so of NHL action).
Dubois stepping up his game this season really benefits the forward group. I think Armstrong is looking to build a forward group with size and physicality, and scoring ability at the wing position, in the mold of our successful 2010 and 2014 teams. If Dubois maintains this level of play he certainly has a very strong chance of making the team, not to mention his pedigree (high draft pick, good World Junior showing, good World Championships performances).
Personally I'd have no issue with Mangiapane on the team. He'd be a likely depth scoring winger that can play bottom six minutes. I'm not sure if I'd want him playing top-6 minutes with McDavid or MacKinnon, but he'd be fine in a depth role.
I wouldn't have Scheifele on the team at this point. He really hasn't done enough I don't think. If Point ends up missing the tournament he's probably on the short list to replace him, but without an injury or two (or if he ups his play) I don't see what he really adds over someone like O'Reilly or Couturier (for a 4th line center role), Stone (versatile 2-way RW), or Point/Stamkos (scoring RW).